Wheeler Reef Adrenalin Dive-Townsville

Transcription

1 Wheeler Reef Adrenalin Dive-Townsville Latitude: S Longitude: 7..7E Date: 5-- Sam Birch SITE DESCRIPTION Wheeler Reef is an outer reef located east of Townsville and is sheltered on one side. It is a green zone in the GBRMP and would be considered one of the most pristine sites in the area due to its high percentage of live coral cover. It is visited by up to liveaboard operations and one day boat times a week and anthropogenic impact is considered low. Dive tourism and anchoring could be considered the main impact. There is one public mooring and anchoring does occur at the site. The reef flat leads to a wall and a number of bommies, canyons and patches of reef surrounded by sand, reaching depths of m and above. There is a large lagoonal area and sand cay. The site exhibits a huge coral coverage and diversity. The shallow transect on the north side of the reef had a larger proportion of sand as the reef was mainly bommies and a wall, whereas the deeper site on the west side of the reef was more consistent reef community. A comparison was not made with data collected in due to insufficient data.

2 SUBSTRATE SURVEY Site Shallow: Wheelr Reef has an extremely high level of hard coral cover with 57.5% noted in the 5m site. 7.5% of this amount is branching Acropora sp. There is 7.5% of Rock with equal levels of turf algae and coralline algae. There is just over % soft coral cover and % of sand on the transect (figures and ). Percent cover + - SE 7 5 Percent Cover of Substrate for Wheeler Reef (Site 5m depth) 5-- HC SC RKC NIA SP RC RB SD SI OT Figure : 57.5% of the substrate is hard coral in the 5m site. Percent cover + - SE 7 5 Percent Cover of Substrate for Wheeler Reef (Site 5m depth) 5-- HC SC RKC NIA SP RC RB SD SI OT OT SI SD RB RCCA RCTA RC SPE SP NIA RKCTA RKCNIA RKC SCB SCZ SCL SC HCB HCP HCE HCM HCF HCBR HC Figure : Branching hard coral dominates the substrate in the 5m site.

3 Site Deep: Just over 7% of the substrate in the 8m site is hard coral, of which 5% is branching hard coral, namely Acropora sp. There was.% of Rock, the majority of this being turf algae. There is only 5.% of sand on the transect (figures and ). Percent cover + - SE Percent Cover of Substrate for Wheeler Reef (site 8m depth) -- HC SC RKC NIA SP RC RB SD SI OT Figure : The hard coral cover is even higher at the 8m site Percent cover + - SE Percent Cover of Substrate for Wheeler Reef ( site 8m depth) -- HC SC RKC NIA SP RC RB SD SI OT OT SI SD RB RCCA RCTA RC SPE SP NIA RKCTA RKCNIA RKC SCB SCZ SCL SC HCB HCP HCE HCM HCF HCBR HC Figure : Similar to the shallow site, the majority of the substrate is branching hard coral.

4 INVERTEBRATES SURVEY Site Shallow: Giant clams are the dominant invertebrate found at the shallow site with a mean abundance of.75 per m. There is a mean abundance of Drupella of.5 and occurrences of Diadema, four sea cucumber species and Crown of Thorns (figure 5). The majority of giant clam sizes are -cm (figure ). 7 Mean Abundance of Invertebrates at Wheeler Reef (Site 5m depth) 5-- Mean Abundance +-SE 5 Banded coral shrimp Diadema Pencil urchin T. ananas S. chloronotus H. nobilis H. fuscopunctata S. variegatus Crown of Thorns Giant clam Tripneustes Triton shell Lobster Trochus Drupella Figure 5: The dominant key invertebrate in the shallow site is the Giant Clam. Distribution of Giant Clams by Size at Wheeler Reef (Site 5m depth) 5-- Mean abundance per m < cm - cm - cm - cm -5 cm >5 cm Giant clams size Figure : The majority of the Giant Clams found at the 5m site were - cm in length.

5 Site Deep: There is a mean abundance of 9.5 Drupella per m at the 8m site and a larger number of Crown of Thorns (mean abundance per m ) than at the 5m site. There were fewer giant clams (mean abundance per m ).See figure 7. Mean Abundance +-SE 8 8 Mean Abundance of Invertebrates at Wheeler Reef (site 8m depth) -- Banded coral shrimp Diadema Pencil urchin T. ananas S. chloronotus H. nobilis H. fuscopunctata S. variegatus Crown of Thorns Giant clam Tripneustes Triton shell Lobster Trochus Drupella Figure 7: The dominant key invertebrate at the 8m site is the coral eating snail Drupella.

6 IMPACTS SURVEY Site Shallow: There is a mean of.5 Drupella scars per m counted at the site and other damage and other scars at approximately 5 counted per m (figure 9). Mean Abundance per m Boat/Anchor damage Mean Abundance of Impacts at Wheeler Reef (Site 5m depth) 5-- Dynamite damage Other damage Trash: Fish nets Trash: General Drupella scars Crown of Thorns scars Other scars Figure 9: Drupella snails proved to be the largest impact in the shallow site. Site Deep: Crown of Thorns Scars, indicating the presence of Crown of Thorns, are the largest impacts with a mean abundance of 5.75 per m followed by Drupella at 5.5 per m. Other scars and other damage had mean abundances of.75 and.5 per m respectively (Figure ) Mean Abundance per m Boat/Anchor damage Mean Abundance of Impacts at Wheeler Reef (site 8m depth) 5-- Dynamite damage Other damage Trash: Fish nets Trash: General Drupella scars Crown of Thorns scars Other scars Figure : Crown of Thorns and Drupella were the largest impacts in the 8m site.

7 BLEACHING Site Shallow: Only % of the coral population in the 5m site was found to be bleached and out of this an average of % of the coral surface was affected by bleaching, namely the upper surfaces of branching Acropora sp.(figure ) There was a greater abundance of bleached corals with less than 5% of their surface bleached (figure ) Estimated Percentage of Coral Population Affected by Bleaching Wheeler Reef Site 5-- Estimated Mean Percentage of Coral Surface affected by Bleaching Wheeler Reef Site % % Bleached Corals (%) Non-bleached Corals (%) 7% % Colony surface bleached (%) Colony surface non-bleached (%) Figure : Estimated percentages of the total coral population affected by bleaching and the surface area affected. Mean number of bleached corals per m Bleached Coral Distribution at Wheeler Reef (Site 5m depth) 5-- <5% 5-5% 5-75% 75-% Percentage surface area that is bleached Figure : A greater number of corals had a smaller area of bleached surface area. Site Deep: The 8m site has less bleaching with % of the coral population showing signs of bleaching and out of this % of the surface was affected.

8 PICTURES Pic.: Two healthy corals competing for space (Wheeler Reef) Sam Birch Pic.: A turtle in the shallows (Wheeler Reef) Sam Birch Pic.: The site is dominated by different forms of Acropora sp. (Wheeler Reef) Sam Birch

9 Pic.: Drupella snails and the resulting scars after the tissue is eaten (Wheeler Reef) Pic.5: DON T KNOW THE NAME!!!! Pic.: Octopus (Wheeler Reef)